George forbes



(No Model.)

G. FORBES.

ELECTRICAL COLLECTING DEVICE.

No. 427,259. Patented May (M1890.

gzjifnesses I Znvenfor 2 j Blj Qfifornm f UNITED STATES PATENT OFFICE.

GEORGE FORBES, OF IVESTMINSTER, COUNTY OF HIDDLESEX, ENGLAND.

ELECTRICAL COLLECTING DEVICE.

SPECIFICATION forming part of Letters Patent No. 427,259, dated May 6, 1890. Application filed November 29, 1889. Serial No. 331,971. (No model.) Patented in England January 29, 1885 .N0. 1,288.

To all ZU7L0777/ it may concern:

Be it known that I, GEORGE FORBES, a subject of the Queen of Great Britain, and a resident of the city of WVestminster, England, have invented a new and useful Improvement in Means for Establishing Electrical Connection between Surfaces in Relative Motion, applicable to the collectors of dynamo-machines, (for which Letters Patent have been secured in Great Britain, bearing number 1,288, dated January 29, 1885,) of which the following is a specification.

My invention has for its object improved means for establishing electric connection between surfaces in relative motion, and is applicable to the collectors of dynamo-machines.

In dynamoanachines generally there is difficulty in making the contact in a satisfactory manner between the movin and the station ary parts of the collector or commutator, and this is especially the case in continuous-current dynamo-machines, in which the current has to be led away from the circumference of a rapidly-revolvin g disk. I have employed mercury for the purpose, and mercury can be used under circumstances in which the application of a metallic brush is unsuitable.

According to my present invention I am able to take off the current from the circumference of such a disk much more conveniently than by either of the methods mentioned above, and thisI do by means of plumbago or hard carbon applied with moderate pressure to the disk. The friction resulting from this contact is small and a very satisfactory electrical connection is established. A convenient way to employ the carbon contact-maker is to set a block of this material into a holder made of copper. Such contactmakers are applicable for use in electric propulsion or wherever contact between a metallic conductor and a contactinaker, the one in movement relatively to the other, is required. They may also be applied in substitution for metallic brushes in ordinary dynamo machines.

By the use of my improved contacts the friction, wearing away, and heating which generally result when contact is made by metal surfaces in relative motion are to a great extent avoided.

Various forms of carbon, either in a nat ural state or manufactured, may be employed. I prefer, however, to employ plates of carbon such as are commonly used in galvanic batteries, and I strengthen them and increase their conductivity by backing them with copper. I apply the copper to the carbon by electro-d eposition, either to the full thickness required or to a suflicient thickness to admit of convenient attachment by soldering or by screws or another metallic support.

\Vhere it is an object to reduce the resistance of the contact as far as may be, I employ as thin a carbon plate as I conveniently can, (one-eighth of an inch will be found suitable,) and I deposit copper over the whole or nearly the whole of the surface, excepting that which actually touches the opposed conductor.

To replace the metallic brushes of ordinary dynamos, I employ carbon slabs, say, of an eighth of an inch in thickness. 1 deposit copper on both the faces, and, if desired, further strengthen the slab by a backing, as already described. in a metal clip, which I fix to the usual brushholder of the dynamo. The carbon slab then takes the place of a metallic brush, and it is used in a similar manner. Its end makes contact with the revolving part of the commutator. It is obvious that the same con- I then clamp the slab firm struction is applicable to the brushes of elec-.

tric motors. These contact-makers can also be employed in electrical railways to take the current for propelling the train from an insulated rail or bar. In this case the current may advantageously be divided between sev eral contact-makers.

Plumbago, either in the pieces or nodules in which it is found in nature or prepared in such a manner as not to seriously impair its conducting property may, when the cost is not too great, be very advantageously employed in contaetanakers according to my invention.

In the accompanying drawings, Figure l is a diagram illustrating an application of the invent-ion, and Fig. 2 is an enlarged detail.

In the iigures, A represents diagrammatic ally a commutator, and B a carbon brush or contactnnakor. In Fi 2 the backing b is shown as screwed to the inner backing l) by the screws 0. lhc backing b may be that applied by electro-deposition, and a similar coating 11 may be applied upon the opposite side of the carbon plate B.

.. I claim as my invention 1. A contact maker or brush for establishing electrical connection with parts in rapid relative motionsuch as the collectors of dynamo-machinesconsisting of a plate of carbon, substantially as described.

2. A contact maker or brush for establishingelectrical connection with a rapidly-moving contact-surface of metal, consisting of a carbon plate.

3. A contact maker or brush for establishingelectrical connection with a rapidly-moving contact-surface, consisting of a plate of carbon backed with metal, substantially as described.

4. In combination with the commutator or GEORGE FORBES.

Witnesses:

FRANCIS W. FRIGOUT, U. S. Deputy Consul-General,London, England.

REGINALD BELFIELD. 

